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Cranial Nerves Flashcards

1
Q

cranial nerves I and II exit

A

the only two that do not exit the brain at the level of the brainstem

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2
Q

cranial nerves III and IV exit

A

exit at the level of the midbrain

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3
Q

cranial nerves V, VI, VII, and VIII exit

A

exit at the level of the pons

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4
Q

cranial nerves IX, X, XI, and XII exit

A

exit at the level of the medulla

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5
Q

pure motor nerves

A

CN IV, VI, XI, and XII

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6
Q

eye movements and pupillary contriction

A

III, IV, VI

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7
Q

pure sensory nerves

A

I, II, VIII

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8
Q

mixed nerves

A

V, VII, IX, and X

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9
Q

parasympathetic fibers

A

III, VII, XI, and X

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10
Q

CN I Olfactory Nerve

A

sensory: responsible for the sense of smell

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11
Q

CN I Olfactory Nerve: path

A

nerve fibers traverse the skull through the cribriform plate where neurons synapse directly with the cortex with no relay through the thalamus

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12
Q

CN I Olfactory Nerve: pathology

A

head trauma can cause damage to the olfactory nerve as it travels through the cribriform plate leading to anosmia
olfactory groove meningiomas can also present with anosmia

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13
Q

CN II Optic Nerve

A

sensory: responsible fort visual sensory input

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14
Q

CN III Oculomotor Nerve

A

motor: innervates numerous extraocular muscles: superior rectus, inferior rectus, medial rectus, and inferior oblique as well as levator palpebrae
parasympathetic: pupillary constrictor and ciliary muscles (efferent limb of the pupillary reflex)

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15
Q

CN III Oculomotor Nerve: pathology

A

oculomotor nerve palsy can present with a combination of four possible clinical features: ptosis, ocular deviation, mydriasis, and diplopia
- ptosis secondary to loss of innervation of levator palpebrae muscle
- ocular deviation (down and out) and diplopia due to unopposed action of the lateral rectus and superior oblique muscles
- mydriasis occurs due to damage to the parasympathetic fibers which supply the pupillary constrictor and ciliary muscles

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16
Q

CN III Oculomotor Nerve: path etiologies

A

include trauma, diabetes, hypertension, subarachnoid hemorrhage, and compression from a posterior communicating aneurysm or uncal herniation

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17
Q

posterior communicating aneurysm

A

compresses the third nerve leading to ipsilateral pupillary dilatation and ophthalmoparesis

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18
Q

CN IV Trochlear Nerve

A

motor: innervates the superior oblique muscle, which is responsible for internal rotation and depression of the eye

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19
Q

CN IV Trochlear Nerve: pathology

A

exits the brainstem dorsally
of the cranial nerves, CN IV has the longest intracranial course
patients will complain of diplopia and difficulty descending stairs
on exam, patients will often tilt their head away from (contralateral to) the affected side to compensate for extorsion of the ipsilateral eye

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20
Q

CN V Trigeminal Nerve exits

A

at the level of the pons and trifurcates into three branches
- V1 Ophthalmic: traverses the skull through the Superior orbital fissure
- V2 Maxillary: traverses the skull through the foramen Rotundum
- V3 Mandibular: traverses the skull through the foramen Ovale
mnemonic: “Standing Room Only”

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21
Q

CN V Trigeminal Nerve

A

sensory: responsible for all modalities of sensation to the face
motor: innervates the muscles of mastication (masseter, temporalis, medial, and lateral pterygoids), tensor veli palati, anterior belly of the digastric, mylohyoid, and tensor tympani
- motor fibers exit via foramen ovale

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22
Q

CN V Trigeminal Nerve: Pathology

A

associated symptoms with a trigeminal lesion include impaired facial sensation and impaired hearing of the ipsilateral ear secondary to damage to the tensor tympani muscle
- can be seen in Wallenberg’s syndrome which is due damage to the lateral medulla from a posterior inferior cerebellar artery (PICA) ischemic stroke

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23
Q

trigeminal neuralgia

A

compression of the trigeminal nerve can lead to trigeminal neuralgia which presents with intermittent, severe sharp/stabbing-like paroxysms of the face, episodes usually occur for only a few seconds at a time
sensory exam normal
common triggers: brushing teeth, washing face, and strong winds
carbamazepine first line therapy

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24
Q

dura of anterior fossa

A

innervated by ophthalmic branch of trigeminal nerve (CN VI)

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25
dura of posterior fossa
predominantly innervated by cervical roots C2 and C3 as well as CN X
26
CN VI Abducens Nerve
Motor: innervates lateral rectus muscle, which is responsible for lateral deviation (abduction) of the eye
27
CN VI Abducens Nerve: pathology
lesion to the abducens nerve will lead to dysfunction of the lateral rectus muscle and the unopposed action of the left medial rectus muscle causing the affected eye to be turned nasally can be secondary to increased ICP
28
CN VII Facial Nerve
motor: innervates the stapedius, buccinator, posterior belly of the digastric, and muscles of facial expression including frontalis, corrugator, orbicularis oculi and oris, nasalis, mentalis, and platysma sensory: responsible for lacrimation, salivation (submandibular, sublingual), taste from the anterior 2/3rds tongue and sensation of the external ear
29
CN VII Facial Nerve: pathology
Bell's palsy is a facial nerve mononeuropathy that presents with acute weakness of upper and lower facial muscles secondary to nonspecific viral infection - most common cause of facial nerve paralysis - second most common is HSV reactivation - treatment: prednisone to reduce inflammation +/- valacyclovir for severe cases infection related facial mononeuropathies often make a complete or near-complete recovery and rarely recur non-infectious causes of facial mononeuropathy include sarcoidosis, diabetes, Sjogren's syndrome, and amyloidosis
30
Ramsay Hunt syndrome
also called geniculate neuralgia or nervus intermedius neuralgia paroxysms of severe pain deep in the ear and can present as hearing loss, bitter taste, tinnitus, and vertigo secondary to viral spread to the vestibulocochlear nerve vesicular rash on external acoustic meatus and lateral tongue
31
ramsay hunt syndrome pathophysiology
herpes zoster virus lies latent in geniculate ganglia after initial infection and reactivation causes inflammation of the nerve within the narrow stylomastoid foramen -> damage to the nerve can cause facial nerve mononeuropathy more seen in immunocompromised patients
32
CN VII Facial Nerve: taste
rarely affected in facial nerve mononeuropathies because taste fibers do not traverse through the stylomastoid foramen facial nerve lesions proximal to the chorda tympani, which are uncommon, could present with a taste deficit on the ipsilateral side
33
CN VII Facial Nerve: hyperacusis
caused by weakness of the stapedius muscle because bone is unable to cover the oval window to protect it from low vibratory tones
34
Lyme disease
can cause unilateral or bilateral facial nerve palsies as well as multiple cranial neuropathies
35
CN VIII Vestibulocochlear Nerve exits
via the internal acoustic meatus
36
CN VIII Vestibulocochlear Nerve
sensory: responsible for auditory sensory input (cochlear nerve) and maintaining equilibrium (vestibular nerve)
37
Auditory Pathway
Spiral ganglion -> Superior olivary nucleus and trapezoid body -> Lateral lemniscus -> Inferior colliculus -> Medial geniculate nucleus -> auditory cortex internal acoustic meatus is SSLIM
38
CN VIII Vestibulocochlear Nerve: pathology
BPPV: otoliths -> nausea and positional vertigo Dx: Dix Hallpike. Tx Epley maneuver
39
brainstem auditory evoked potentials (BAEPs)
cochlear nerve represents wave I if wave I is present without any other waveforms on BAEPs then this is concerning for brain death
40
unilateral peripheral vestibular dysfunction
patient falling towards the affected ear
41
CN IX Glossopharyngeal Nerve
motor: innervates stylopharyngeus sensory: responsible for taste of posterior 1/3 tongue, salivation (parotid), and autonomic monitoring via chemo- and baroreceptors of the carotid body and sinus
42
baroreceptor reflex
essential in regulating responses to blood pressure changes through changes in sympathetic tone. when blood pressure drops, baroreceptors cause an increase in sympathetic drive to increase heart rate in an attempt to preserve perfusion to the brain. central locations in the aortic arch and carotid sinus - aortic arch baroreceptor information travels to the nucleus tractus solitarius, and then to the ventrolateral medulla, via the aortic nerve (Nerve of Cyon), which combines with the vagus nerve (CN X) - carotid sinus baroreceptor information primarily reaches these same nuclei via the glossopharyngeal nerve (CN XI)
43
CN IX Glossopharyngeal Nerve: pathology
glossopharyngeal neuralgia - presents with intense and paroxysmal pain of the ear and tonsillar fossa which can be triggered by coughing or swallowing - syncope can occur due to inappropriate carotid sinus/body sensory fiber activation
44
most commonly asked cranial nerve-muscle innervation associations:
CN IV: superior oblique CN VI: lateral rectus CN V: anterior belly of the digastric and tensor tympani CN VII: posterior belly of the digastric and stapedius CN IX: stylopharyngeus
45
CN X Vagus Nerve
motor: innervates the muscles of the pharynx and larynx, and only one tongue muscle: palatoglossus sensory: responsible for taste sensation of the epiglottis as well as visceral sensation of the heart, lungs, and GI tract
46
CN X Vagus Nerve: path
derives fibers from the nucleus ambiguus, the dorsal motor nucleus, and the nucleus solitarius nucleus ambiguus -> branchial motor fibers that travel to the muscles of the pharynx and larynx dorsal motor nucleus -> parasympathetic innervation to the heart, lungs, and GI tract nucleus solitarius -> taste and visceral sensory information from the heart, lungs, and GI tract
47
CN X Vagus Nerve: pathology
recurrent laryngeal nerve is a pure motor branch of the vagus nerve which innervates the laryngeal muscles. - damage to this nerve by trauma, thyroid surgery, or compression neoplasm can lead to hoarseness, dysphagia, and hypophonia
48
CN XI Spinal Accessory Nerve
motor: sternocleidomastoid and trapezius
49
CN XII Hypoglossal Nerve
motor: innervates the extrinsic muscles of the tongue (glenioglossus, hypoglossus, and styloglossus)
50
CN XII Hypoglossal Nerve pathology
lesion will lead to tongue deviation toward the pathologic side
51
Cavernous sinus includes
several cranial nerves: CN III, IV, VI, V1 and 2, and sympathetic nerve fibers internal carotid artery surrounds pituitary gland
52
Cavernous sinus pathology
CN VI is the closest to the ICA and is most likely to be damaged in carotid dissection
53
Cavernous Sinus Syndrome
presents with papilledema, proptosis, and painful ophthalmoplegia - proptosis secondary to occlusion of ophthalmic veins common cause is cavernous sinus thrombosis often secondary to infection from orbital cellulitis or sinusitis diabetes is risk factor
54
cribriform plate
olfactory nerve
55
optic canal
optic nerve
56
superior orbital fissure
oculomotor, trochlear, abducens, ophthalmic branch of trigeminal
57
foramen rotundum
maxillary branch of trigeminal
58
foramen ovale
mandibular branch of trigeminal
59
internal auditory meatus
facial nerve and vestibulocochlear nerve
60
jugular foramen
glossopharyngeal, vagus, and spinal accessory
61
hypoglossal canal
hypoglossal nerve
62
foramen magnum
ascending fibers of spinal accessory nerve enter before exiting the jugular foramen also contains medulla and vertebral arteries
63
foramen lacerum
contains greater petrosal and deep petrosal nerves internal carotid artery runs along, but not technically through, this foramen
64
foramen spinosum
middle meningeal artery/vein and meningeal branch V3
65
corneal reflex
protective blink response afferent limb: ophthalmic division of trigeminal nerve efferent limb: facial nerve (VII) which innervates orbicularis oculi
66
pupillary reflex
constriction of both eyes in response to light afferent limb: optic nerve -> pretectal nucleus -> bilateral Edinger Westphal nuclei efferent limb: oculomotor nerve - Edinger-Westphal nuclei -> preganglionic parasympathetic fibers to cilliary ganglia via oculomotor neuron -> postanglionic parasympathetic fibers to sphincter muscle of the iris and ciliary muscles both ipsilateral and contralateral pupillary constriction can give insight into the integrity of the oculomotor nerves
67
pupillary reflex pathology
any lesion to the optic nerve can cause loss of both direct and consensual response lesion to the ipsilateral oculomotor nerve and/or Edinger-Westphal nucleus leads to loss of direct pupillary reflex lesion to the contralateral oculomotor nerve and/or Edinger-Westphal nucleus leads to loss of consensual pupillary reflex
68
baroreceptor reflex
helps regulate blood pressure by detecting changes via a baroreceptor located in the carotid sinus and aortic arch. Increased pressures marked by these receptors produce slower heart rates and drops in blood pressure. A decrease in blood pressure produces an increase in sympathetic tone and a decrease in parasympathetic tone. afferent limb is the glossopharyngeal nerve for the carotid sinus and the vagus nerve for the aortic arch. efferent limb is the vagus nerve (CN X).
69
gag reflex
afferent limb: glossopharyngeal nerve efferent limb: vagus nerve
70
nucleus tractus solitarius
both taste (rostral nucleus) and baroreceptor (caudal nucleus) information CN VII: taste to anterior 2/3 tongue CN IX: taste to posterior 1/3 tongue and baroreceptor from carotid sinus CN X: taste to the pharynx and baroreceptor from aortic arch information travels to the VPM of the thalamus
71
nucleus ambiguus
corticobulbar input is bilateral motor fibers to pharynx/larynx/palate via CN IX, X, and XI
72
superior salivatory nucleus
parasympathetic supply to oral and nasal cavity lacrimal and mucosal glands, via CN VII
73
inferior salivatory nucleus
parasympathetic supply to the parotid gland, via CN IX remember that although CN VII runs through the parotid gland physically, the gland's parasympathetic innervation comes from CN IX

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